It is known that, under such conditions, the weight of the body is distributed on all the supporting points of both arches of the foot. Each foot has three supporting points, two at the front (heads of the first and fifth metatarsian) and one at the rear (posterior tuberosities of the calcaneum). In the biped equilibrium position on a plane and horizontal ground, the weight of the body is applied by half on each keystone of the arch of the foot, center of the instep, located plumb with the extension of the front edge of the leg, before then being distributed by half on the anterior supporting points and the posterior supporting point of the arch of the foot. In such a vertical upright position, the centre of gravity of the human body (third lumbar vertebra) and the line of gravity are properly placed, the base of support (contour of the feet and space between the feet) is determined, the lower limbs are in the extension of the trunk and the curvatures of the vertebral column attain their characteristic shape. Under these circumstances of biped equilibrium, the weight of the body is distributed in four quarters on the plantar supporting points. Each forefoot and hind foot receives the quarter of the total weight of the body.
In a known way, a comfortable and static standing equilibrium on the plantar supporting points is made possible by the architecture of the human body, the skeleton, the tendons, the soft parts. Under these conditions, the muscular activity of the trunk and of the lower limbs is low. The obtained equilibrium is passive, transient and unstable.
It is known that as soon as there is a loss of equilibrium, i.e. a risk of falling and regardless of the direction, compensating reflex muscular contractions, postural tonus, reestablish equilibrium. Once equilibrium is reached, the activity of anti-gravitary muscles then ceases until the next loss of equilibrium. The muscular activity of the trunk and of the lower limbs is low. The obtained equilibrium is passive, transient and unstable.
Moreover, it is well established that in all the biped vertical crouching positions, flexed lower limbs, unlocked joints, equilibrium is maintained by means of the powerful action of anti-gravitary muscles of the lower limbs and of the column. Under these conditions, the centre of gravity is lowered, equilibrium is more stable, the line of gravity passes through the centre of each instep, the arch of the foot collapses, the length of the feet increases. The supporting points slightly slide, those of the front towards the front of the foot, those of the rear towards the rear of the foot, and the distribution of the weight of the body on the supporting points is the same as in the vertical standing position. The lower the crouching positions, the more the equilibrium is stable and the higher is the tonus of anti-gravitary muscles. In the full crouching position, the centre of gravity is at its lowest point, the equilibrium is very stable, the body folded over itself assumes a fetal form, knees forwards, buttocks rearwards, head forwards, column bent forwards over the whole of its length (the different lines of column curvature vanish), and the activity of the anti-gravitary muscles ceases. The distribution of the weight of the body on the plantar supporting points remains unchanged. This position is a relaxation posture of the body adopted by children and many adults in certain countries.
It is the central nervous system which provides and regulates muscular postural tonus, from propioceptive sensorial information (muscles, tendons, joints), from vestibular (labyrinths) and exteroceptive visual, auditive and tactile information which it receives. In order to reach the state of equilibrium, the application of a complex system with several inputs (sensorial stimulations) and several outputs (muscular reactions) is required. Any change in stimulation (input) causes a dynamic re-equilibration reaction (output). The result is a harmonious and effective posture.
It is known that any movement starts from equilibrium and reaches it. It is also known that the three exteroceptive sensitivities (sight, hearing, plantar touch) in relation with the outside world, act on the postural tonus by adjusting our attitudes and that the sensitivity of the plantar tactile receptors play a major role here. Submitted to the pressure of the weight of the body and to its variations on the one hand, in contact with the ground, to its texture, its irregularities, its level differences on the other hand, the receptors of the plantar tactile corpuscles, by the amount of information which they detect and transmit to the nervous system, are the starters of reflexes ensuring equilibrium.
The plantar touch organ is a sensorial organ, the acuity of which is essentially sustained by walking and crouching. Walking, a symmetrical natural locomotion, provides the advantage, during the phase of foot progression on the ground, of stimulating in turn the tactile perception of each plantar supporting point. Biped crouching strongly activates perception of all the plantar supports during the changes in flattening of the arches of the feet. Since about fifty years, our way of life has changed, which has caused a reduction in the daily walking time below a threshold which is absolutely required for sustaining the perception of the tactile sensitivity of our plantar supports and the ensuing vertical postural reflexes. The increasingly sedentary (sitting) human being of modern societies gradually loses, without being aware of this, perception of his/her plantar supports concurrently with the loss of his/her vertical postural tonus and of the habit of walking in a natural way.
Abnormal and frequent wear of shoe soles (for example only at the heel) is a sign of deficient supports during ambulation: little or no pressure on certain supports and too much pressure on other ones. Accordingly, the equilibrium reflexes are perturbed. Some of these reflexes are not so well activated and lose dynamic efficiency. The tonus of certain anti-gravitary muscles (lower limbs and column) decreases. By losing tonus in the lower limbs (mainly in thighs) crouching becomes painful. Numerous are those which give up. By lack of sustaining sensitivity of plantar supports (notably by walking and crouching), perception of the sensitivity, postural dynamism, coordination of gestures (any gesture starts from one or more plantar supporting points), suppleness and harmony of the shape of the body gradually disappear, obesity symptoms appear at the same time. Confronted with this established fact, it is recommended by all physicians to monitor one's weight and to move, walk or practice a sports activity.
A subject matter of the invention, by reactivating perception of the tactile sensitivity of all of one's plantar supports, dynamic starters of the vertical posture, is to give the possibility to the human having become sedentary, of not only moving, walking, crouching or practicing a sport safely, but also to give him/her back the desire to do this, and of thereby sparing him/her the risks of obesity.
A subject matter of the invention is to give a user the possibility of focusing on the distribution of the weight of his/her body on his/her plantar supports in a situation of verticality (supported on a plane, mobile surface), by having him/her become aware of his/her disequilibrium.
In the prior art, systems with two mobile plates are known with which the distribution of the user's weight on each of his/her legs may be viewed.
Document WO 87/01923 of the same inventor, discloses an apparatus with a single movable plate mounted on springs and provided with an indicator of horizontality of this movable plate. With this apparatus, the user is able to actively correct the weight-bearing supports of both of his/her feet in order to reach equilibrium, which may be viewed by means of the horizontality indicator of the plate. A bubble level allows accurate indication of when equilibrium is attained.
It is possible to insert scales in a recess of the apparatus described in document WO 87/01923. With the resulting assembly, it is then possible to constantly indicate the weight while the user may continue to improve his/her weight-bearing supports on the mobile plate. A drawback of this known apparatus is that the indication of equilibrium is not interactive and insufficiently arouses the desire of the user to adopt good postures for which equilibrium is reached.
In quite another field, the use of slabs with a resistance which depends on force, so-called FSR (Force Sensitive Resistance) slabs, is known, provided with one or two analog outputs at 3 points in order to be connected to a processing-conversion module which is used for interpreting movements of the human body. The slabs with two analog outputs are sensitive to the posture of the individual on the slab, and more specifically to the distribution of his/her weight in space. They are totally independent of the actual weight, so that they may exactly react in the same way with a child or with a 90 kilogram person. These slabs are, for example, used for forming a sensitive ground with the purpose of modulating sounds and lights, for example.
However, these FSR slabs are neither used nor usable for establishing equilibrium diagnoses.
Document FR 2619702 discloses a plate which is made movable, relatively to a system placed on the ground, by means of a single ball-joint link. The information or response provided by the apparatus is static and is especially perceived visually. A global movement of rotation is alone generated by the ball-joint link in order to oppose the equilibrium of the patient, which strongly limits the stimulation of the tactile perception of the plantar supports.
The objective of the present invention is therefore to overcome one or more of the drawbacks of the prior art by defining an apparatus provided with additional indicator functions which may be activated depending on whether equilibrium is reached or not, the apparatus remaining of simple design and with which the equilibrium in the distribution of the weight on the plantar supports may be specifically accounted for.